The present invention relates material purification. The material can be any material either used in its elemental form, chemical compounds, and their combinations in the form of an alloy. The purified material will be used for product fabrication, casting of various shapes and sizes, as well as raw material for growing crystals.
Purity of the material and compositional uniformity are some of the most important characteristics in crystal growth and product performance. The quality of final products are controlled at the beginning by carefully purifying, precisely doping and controllably mixing elements to produce crystals and alloys of known quality and predictable characteristics.
Needs exist for improved purification and treatment of materials in powder and molten and solid states.
The present invention provides methods and apparatus for ultra purification of materials.
The present invention provides improvements for precisely controlling purity, quality, uniformity and chemical composition of crystals and alloys.
Powder is dispensed on a porous gas distributor in a reduced pressure chamber at a first station. Drying and reactive gases flow through the porous distributor and through the powder. Ultra purification takes place by drying and reactive gas treatment. The powder is transferred into a second station. In another embodiment, the temperature of the first part is increased so that melting occurs. Purification continues following melting. The molten material is transferred into a second station, which is a liquid purification chamber, either by conveyor or by gravity directed flow by tilting of the first section. Purification by reactive gas treatment continues. The liquid purification chamber may be placed at a lower position and have volume suitable to accommodate the liquefied material from the first station. The liquid purification chamber is contained within the same or a separate reduced pressure chamber. A pump or pumps withdraw the reactive gas and impurities are thereby carried out of the powdered or molten material. A dopant controller allows for controlling the dopant level, if any.
When the chamber is filled to a desired level, the liquid material purification process begins. Reactive gases, liquid or solid materials are used during this cycle. This cycle may be a follow-up cycle or parallel cycle to the one for powder purification. Reactive gases are introduced through a porous distributor. When appropriate material properties have been obtained, the liquefied material may be doped and transferred to a third station or chamber, which is a purified liquid-receiving chamber. The third chamber may be at the same level or at a lower level for gravity flow transfer. The third chamber may be either:
a crystal growth crucible;
a molten material storage for continuous casting or crystal growth; or
a chamber for casting the material in certain shapes and sizes.
All chambers may have tilt mechanisms for providing for easy material transfer from one chamber into the next in controlled flow. All chambers may be in one large vacuum chamber or in separate vacuum chambers that allow for material transfer and handling.
Several purification stations may feed the cast/refill/crystal grower, either to provide continuous operation or to provide a proper mix of distinct elements or compounds to form molten material for various alloy products. The mixing may be at the beginning or may be continuous to ensure proper element ratio in the alloy and constant dopant level, if any, in the alloy.
Purification station cascades may be employed for specific applications.
One purification station has a vacuum chamber containing a cylindrical or other rotating porous gas distributor, a material supply line, a gas supply line, a dopant supply line, a vacuum line, heaters, a tilting mechanism, a rotation mechanism, a liquid dispensing line, a control panel for all of the above, and other control data related issues.
The material to be purified is supplied through the supply line. After a required quantity has been introduced, the processing of the material begins. Drying and chemical treatment of the material, as well as doping and mixing of all components, is accomplished during this step.
When the purification has been completed, the material may be transferred to a crystal growth crucible or other applications having need of the purified material.
The material may be subjected to a melting and purification process in its molten state. If the space allows, more material may be added to achieve a certain melt level in the chamber. When all the material has been melted and outgassed, the purification procedure is conducted. If the final product to be delivered needs dopant, suitable amounts of dopant and reactive materials are added to the melt. The rotation of the chamber containing the material provides for proper mixing of the reactive materials and/or the dopant.
When the material has the desired properties, it is delivered to a casting station or to a refilling station, or directly to a crystal grower for batch or continuous crystal growth.
Multiple cascade purification stations may be employed to achieve increased levels of purity of single elements or single compounds, or to form special alloys and to maintain desired single element quality, single compound quality and/or alloy quality and composition.
The purification station cascade can be enclosed in one vacuum chamber, or each station can be enclosed in a separate vacuum chamber. Means of material transfer are used to move material from one station to another or to an application such as crystal grower, casting station or other not specified application.
Purification station cascades may be used in the Pandelisev Crystal Grower (U.S. Pat. No. 5,993,540) or in a Standard Bridgman-Stockbarger approach, or in a Bridgman-Stockbarger process employing an embedded purification station.
Embedded purification station cascade consisting of plurality of purification stations may be considered for certain applications. They can be all housed in a separate vacuum chambers and will have the capability to communicate the material from one station to another in a controlled manner. Or they can be placed one adjacent to another in horizontal or vertical or semi-vertical arrangement within a large vacuum chamber or within the chamber of crystal grower having Bridgman-Stockbarger or Pandelisev (continuous or batch type) crystal grower.
The invention provides methods and apparatus for producing ultrapure materials. The fist station has a chamber and a porous gas distributor in the chamber. The chamber may have elliptical, hexagonal and may be rectangular of having conical or truncated cone shape. A material supply supplies material to the chamber. A gas source connected to the porous distributor supplies gas to the distributor and through the distributor to the material in contact with the distributor. A heater(s) adjacent to the chamber heats the material as gas is passed through the material. One or more discharge ports on the bottom and/or the sides of the chamber discharges the treated material from the first station into a second purification station, material storage or to crystal growth crucible for continuous or batch type growth of single crystal or casting applications. A dopant controller supplies/controls the dopant levels of the material. A treatment liquid or solid supply supplies treatment liquid or solid to the material.
A second station is positioned adjacent or under the discharge of the first station. The second station has a chamber and a porous gas distributor in the chamber. The chamber may have elliptical, hexagonal and may be rectangular of having conical or truncated cone shape. Through the discharge port(s) of the first station material is supplied to the second chamber. A gas source connected to the porous distributor supplies gas to the distributor and through the distributor to the material in contact with the distributor. A heater(s) adjacent to the chamber heats the material as gas is passed through the material. One or more discharge ports on the bottom and/or the sides of the chamber discharges the treated material from the first station into a second purification station, material storage or to crystal growth crucible for continuous or batch type growth of single crystal or casting applications. A dopant controller supplies/controls the dopant levels of the material. A treatment liquid or solid supply supplies treatment liquid or solid to the material.
A third purification station, material storage or a crystal growth crucible for continuous or batch-type growth of single crystal or casting applications may be placed adjacent or under the second station.
Multiple first stations may discharge multiple materials into a second station. Multiple second stations may discharge molten material into the third station crucible.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings.